Twenty patients with a long history of uncontrolled seizures had a complete examination, skull films, brain scan, EMI scan, and daily objective toxicity battery. Video recording and long-term telemetered EEGs established a seizure diagnosis in every patient. On admission, half of the patients exhibited medication toxicity, and half had poor seizure control. During hospitalization, phenytoin, phenobarbital, and primidone levels were determined daily. Carbamezepine, ethoduximide, and sodium valproate levels were measured less frequently. Efforts were made to obtain maximum therapeutic levels without toxicity. Of the patients who earlier exhibited medication toxicity, 3/4 became completely free of side effects. Most of these with poor seizure control on admission were improved. Intensive monitoring techniques make possible better diagnosis and improved treatment of patients with intractable epilepsy.